This revised application requests funds to purchase a gamma irradiator for use by UMDNJ investigators involved in PHS-funded research. As necessary, and approved by the internal advisory committee, this piece of equipment will also serve the needs of other UMDNJ investigators whose projects are funded by non-PHS awards. As detailed in subsequent sections of this application, the existing equipment for irradiation of small animals, tissues and cells is inadequate in primary users. The dose delivery variability within the chamber and mechanical deficiencies of the existing unit further compromise the accuracy of the irradiator. Thus, a replacement unit with a larger sample chamber, attenuators to regulate dose rate, and accessories to facilitate irradiation of animals and cells is sorely needed to enhance the efficient progress of PHS-funded research at UMDNJ-NJMS. The proposed location of the new irradiator within the Research Animal facility, which has a key- card access system after regular working hours, will facilitate its availability to users at all times.